This invention relates in general to anesthetics and in particular to a new and useful anaesthetics evaporator having an evaporating chamber flow conducted through an evaporating chamber and a by-pass flow conducted parallel thereto.
The invention relates to a anaesthetics evaporator with an evaporating chamber flow conducted through the evaporating chamber and a by-pass flow parallel thereto, with concentric setting and regulating devices in both lines, the regulating device compensating for the action of temperature upon the composition of the gas mixture.
In anaesthetics evaporators, the gas flow conducted through them is enriched with the anaesthetic contained in the evaporator to a desired concentration. The gas flow conducted through the anaesthetic evaporator is divided into two partial flows, the by-pass flow and the evaporating chamber flow. Both partial flows are regulated relative to each other in an exact flow ratio by valves, at least one of which is adjustable to change the concentration. The evaporating chamber flow is conducted through an evaporating chamber which generally also contains the supply of liquid anaesthetic, and enriched therein with the anaesthetic in accordance with the vapor pressure which is temperature respondent, dosed, and reunited with the similarly dosed by-pass flow which consists of the other part of the gas flow in an unaltered gas composition. The ratio of the two partial flows results in a gas mixture with the desired anaesthetics vapor concentration.
Due to the dependence of the vapor pressure on the temperature of the liquid anaesthetic there results a temperature-dependent concentration. In order to render this dependence ineffective, which would alter the mixing ratio greatly, particularly due to the heat loss originating during the evaporation, known anaesthetics evaporators have temperature compensation devices.
One known anaesthetic evaporator has a regulator, located in the by-pass and consisting of parts disposed in both the evaporating chamber flow and the by-pass flow and made of materials of different coefficients of thermal expansion, forming an annular gap in the by-pass which changes as a function of temperature. The height of the annular gap thus determines the gas flow in the by-pass (German PS 25 07 261).